forces and their effects

Question 1

describe how objects can interact:
a) at a distance without contact

Answer 1

• non contact forces are caused by interacting fields (gravitational attraction caused by gravitational fields interacting)
• interacting magnetic fields cause attraction or repulsion between magnetic objects
• electrostatic force causing attraction and repulsion between electrical charges is due to interactions between their electric fields

Question 2

describe how objects can interact:
b) by contact, normal contact force and friction

Answer 2

exert forces on each other like friction

Question 3

describe how objects can interact:
c) producing pairs of forces (which can be presented as vectors)

Answer 3

• two objects interact and both feel an equal but opposite force (Ns 3rd law)
• this pair of forces = interaction pair
• can be represented by vectors
  (ex chair pushes on ground, ground pushes on chair)

Question 4

an example of an object that interacts at a distance without contact

Answer 4

1. magnetic force = magnetic material in a magnetic field
2. electrostatic force = charged particle in an electric field
3. gravitational force experienced in a gravitational field, masses attracted towards each other by gravitational force

Question 5

example of contact force

Answer 5

1. any touching object
2. friction between car’s tyre and the road

Question 6

explain the difference between vector and scalar quantities

Answer 6

vector = magnitude and direction (ex velocity, force, speed)
scalar = magnitude only, no direction (ex mass)

Question 7

how to make a scale drawing

Answer 7

1. draw all forces on an object to scale
2. draw straight line from first force to last force (=resultant force)
3. measure length of the resultant force on the diagram to find the magnitude of the force and angle to find its direction

Question 8

what do free body force diagrams show

Answer 8

an object and all the forces acting on it

Question 9

free body diagrams should:

Answer 9

• include every force acting on object
• no forces it exerts
• sizes of arrows show the relative magnitudes of forces
• direction show the directions of forces

Question 10

what happens to balanced forces when the resultant force is zero

Answer 10

• the resultant force is zero means the object in equilibrium
• N’s 1st law - stays

Question 11

explain forces acting on an isolated solid
object or a system where several forces lead to a
resultant force on an object

Answer 11

• if there’s a number of forces acting at a single point you replace them with a resultant force

Question 12

how a normal contact force works with an objects equal to each other’s weight

Answer 12

• forces act in opposite direction so no resultant force in vertical direction

Question 13

how frictional force acting on a van is smaller than the driving force

Answer 13

• pushes it forwards
• is a resultant force in the horizontal direction

Question 14

how to reduce unwanted energy transfer through lubrication

Answer 14

• lubricant reduces friction
• so making it more efficient